1. Field of the Invention
The present invention relates to an insulating oxide or oxynitride and a semiconductor device that uses the same.
2. Description of the Related Art
A method has been employed for increasing a capacitance by decreasing a thickness of a gate insulating film in order to secure a sufficient quantity of charges that are induced in a channel of a metal insulator semiconductor field effect transistor (MISFET). As a result, an SiO2 film, which constitutes the gate insulating film, has been thinned more and more, almost down to a value much less than 1 nm.
With such a thin SiO2 film, a gate-leakage current has become so large that power consumption cannot be suppressed due to waste of standby power. For example, with the thickness of the SiO2 film being 0.8 nm, the gate-leakage current reaches 1 kA/cm2, which is a significant problem in terms of power consumption.
To decrease the power consumption, it is effective to increase the thickness of the film. It has been therefore discussed to use a high-dielectric constant (high-k dielectric) material as an insulating film that can secure a sufficient quantity of charges even if it is thicker than the SiO2 film. As such high-k dielectric and stable materials, a lot of metal oxides and metal oxynitrides are known.
As insulating films having these properties, in particular the following promising candidates are enumerated presently: HfO2, ZrO2, silicate films of these (HfSiO, ZeSiO), and aluminate thin films (HfAlO, ZrAlO), nitrides of these (HfON, ZrON, HfSiON, ZrSiON, HfAlON, ZrAlON), etc.
Besides, such a thin film may be a good candidate as to have a layered perovskite structure, which provides a high-dielectric constant substance. The following will give a few examples of the perovskite structure. The example may include materials composed of a substance which has an ABO3 structure whose A-site is selected at least one from a group of plus-divalent substances of Mg, Ca, Sr, and Ba and whose B-site is selected at least one from a group of plus-tetravalent substances of Ti, Zr, Hf, Ce, C, Si, Ge, and Sn and its nitrides. More specifically, they are, for example, SrTiO3, BaZrO3, CaHfO3, (Ba, Sr) (Ti, Zr)O3, etc.
Besides, an example may include materials composed of a substance which has an ABO3 structure whose A-site and B-side are each selected at least one from a group of plus-trivalent substances of Sc, Y, La, B, Al, Ga, In, and Tl, and a lanthanoid group of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu and its nitrides. More specifically, they are, for example, YAlO3, LaAlO3, YScO3, LaScO3, PrScO3, NdScO3, SmScO3, EuScO3, GdScO3, TbScO3, DyScO3, HoScO3, ErScO3, TmScO3, YbScO3, LuScO3, (La, Y) (Al, Sc)O3, etc. as promising candidates. This group of materials whose A-site and B-site are both made of a plus-trivalent substance has a relatively large band gap (5 to 7 eV) and a large relative dielectric constant (15-40) and so provides a well-balanced film as a gate insulating film.
Further, materials having a pyrochlore structure are also promising. That is, they may include materials composed of a substance which has an A2B2O7 structure and whose A-site is selected at least one from a group of plus-divalent substances of Mg, Ca, Sr, and Ba and whose B-site is selected at least one from a group of plus-pentavalent substances of V, Nb, Ta, P, As, Sb, and Bi and its nitrides. More specifically, Sr2V2O7, Sr2Nb2O7, etc. are promising candidates.
Besides, they may include materials composed of a substance which has an A2B2O7 structure and whose A-site is selected at least one from a group of plus-trivalent substances of Sc, Y, La, B, Al, Ga, In, and Tl, and lanthanoids such as La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu and whose B-site is selected from a group of plus-tetravalent substances of Ti, Zr, Hf, Ce, C, Si, Ge and Sn and its nitrides. More specifically, La2Zr2O7, La2Hf2O7, Y2Zr2O7, Y2Hf2O7, etc. are promising candidates.
However, high-dielectric constant metal oxides have a problem of easily containing an oxygen defect.